if c = 's'
          then
              begin
                 if c = 's'
                         then write('Vysledek je: ', a+b)
                         else write('Spatne zadani operace');
                         end;

           if c = 'o'
                     then write('Vysledek je: ', a-b)
                     else write('Spatne zadani operace');
                     end;

           if c = 'n'
                      then write('Vysledek je: ', a*b)
                      else write('Spatne zadani operace');
                      end;